1. Technical Field
The present invention relates to a method of manufacturing a semiconductor device.
2. Related Art
Referring to FIGS. 6A to 6C, a conventional interconnect formation process will be reviewed. Firstly an insulating film 121 and a conductive film 131 are sequentially formed on a semiconductor substrate 101. The insulating film 121 may be an oxide film formed through a thermal oxidation process, and the conductive film 131 may be a polycrystalline silicon film formed by CVD (Chemical Vapor Deposition). Then a photoresist 141 is laid over the conductive film 131, and a pattern is delineated on the photoresist 141 by photolithography (FIG. 6A). Here, the space width of the photoresist is equal to the line width d.
Then a dry etching process is performed on the conductive film 131 utilizing the photoresist 141 as the mask (FIG. 6B). After removing the photoresist 141, an insulating film 122 constituted of an oxide film, which serves as an interlayer dielectric, is formed for example by CVD. That is how an interconnect constituted of the conductive film 131 is formed (FIG. 6C).
In addition, Japanese Laid-open Patent Publication No. 2002-280388 (referred to as “Patent Document 1” below) discloses an interconnect formation process. The interconnect formation process according to Patent Document 1 will be described referring to FIGS. 7A to 7C and 8A to 8C. Firstly an insulating film 121, a conductive film 131, and another insulating film 123 which is an oxide film, are sequentially formed on a semiconductor substrate 101. Then a photoresist 141 is laid over the insulating film 123, and a pattern is delineated on the photoresist 141 by photolithography (FIG. 7A). Here, the space width of the photoresist 141 is three times of the line width d.
Then an etching process is performed on the insulating film 123 utilizing the photoresist 141 as the mask (FIG. 7B). After removing the photoresist 141, an insulating film 161 constituted of a nitride film is formed all over the substrate, and the insulating film 161 is etched back by anisotropic etching, so as to expose a surface of the conductive film 131 (FIG. 7C).
The insulating film 123 which is an oxide film is then removed (FIG. 8A), after which an etching process is performed on the conductive film 131 utilizing the insulating film 161 as the mask (FIG. 8B). After removing the insulating film 161, an insulating film 124 constituted of an oxide film; which serves as an interlayer dielectric, is formed for example by CVD. At this stage, an interconnect constituted of the conductive film 131 is formed (FIG. 8C).